Temporal data support was introduced in the SQL:2011—ANSI standard. There were also attempts to define support in the previous standard versions, but without success (TSQL2 extensions in 1995). They were not widely accepted and vendors did not implement them.
The SQL:2011 standard proposed that temporal data should be supported in relational database management systems. A very important thing is that SQL:2011 did not introduce a new data type to support temporal data; rather, it introduced the period.
A period is a table attribute and it's defined by two table columns of date type, representing start time and end time, respectively. It is defined as follows:
- A period must have a name.
- The end time must be greater ...
